Conventionally, as a ROM (read only memory) recording medium of digital information and an information reproducing apparatus thereof, there are a CD (compact disk) and a player of the same.
FIG. 28 is a block diagram schematically showing that apparatus.
In FIG. 28, reference numeral 100 is a CD and reference numeral 200 is a player.
In the CD 100, pits 102 are formed as digital information in a signal layer 101. A protective layer 103 and a transparent plastic substrate 104 are adhered to an upper surface and a lower surface of this signal layer 101.
In such a CD 100, the track pitch is set to 1.6 .mu.m and the shortest pit length is set to 0.9 .mu.m.
The player 200 is an apparatus which detects the existence of the pits 102 to reproduce the information of the CD 100 and is provided with an optical pick-up 201, an RF amplifier 202, a digital signal processing circuit 203, and so forth.
Namely, a laser beam L having a wavelength of 780 nm is fired from a laser diode 210 of the optical pick-up 201 to the CD 100 side. The reflected laser beam L is detected at the photodiode 211. The RF signal is amplified by the RF amplifier 202, then subjected to digital processing and so forth at the digital signal processing circuit 203 to reproduce the information of the CD 100.
The CD 100 and the player 200 thereof described above, however, are structured to use a laser beam L to optically detect the pits 102 of the CD 100; therefore, there is a limit to the wavelength of that beam and the precision of detection is low. For this reason, the size of the pits 102 cannot be made small and a large amount of information cannot be recorded on the CD 100. For example, in a CD 100 having a diameter of 12 cm, the recordable amount of digital information is about 650 megabytes.
Further, as other recording media and the information reproducing apparatuses thereof, there are the recently much talked about DVD (digital video disk) and the players thereof.
In this apparatus, the track pitch of the DVD is set to 0.84 .mu.m and the shortest pit length is set to 0.451 .mu.m, so the existence of the pits can be detected by a laser beam having a wavelength of 635 nm or less. Accordingly, a higher density and larger amount of information can be recorded on a DVD in comparison with the CD 100. Nevertheless, the amount of digital information which can be recorded on a DVD of a diameter of 12 cm is about 3.9 gigabytes.
Contrary to this, when the information of the CD and DVD is detected by using a laser beam having a blue wavelength, the precision of detection is improved. However, since the pits are detected by using light, there is a limit and thus only information of a magnitude of 0.45 .mu.m to 0.3 .mu.m at the lowest can be detected.
Accordingly, the conventional recording media such as CDs and DVDs and the information reproducing apparatuses using the same were insufficient as multimedia apparatuses, for which recording and reproduction of a large amount of information such as moving picture information and audio information were required.
On the other hand, as a recording medium which can be recorded on and reproduced from like a nonvolatile memory of a semiconductor and an information recording and reproducing apparatus thereof, there are a so-called "Mini Disc" and a player thereof.
The "Mini Disc" recording medium is a magneto-optic disk 300 as shown in FIG. 29 and is structured with a. magnetic layer 302 formed on a polycarbonate substrate 301 in a corrugated manner and with a protective layer 303 provided on the magnetic layer 302.
When recording, the laser beam strikes the recording medium and heats the same while an external magnetic field is applied, the magnetization is inverted and information of "1" or "0" is recorded according to the orientation of the domain. Then, when reproducing, using the fact that the plane of polarization of the reflected light of the laser beam slightly rotates in a forward or reverse direction corresponding to the orientation of the magnetization of the magnetic layer (i.e., the Kerr effect), the laser is irradiated, a laser beam is fired to read the orientation of the magnetization.
In the "Mini Disc" as well, however, since light is used for the sensing medium, it is not possible to exceed the limit of the wavelength of light. As shown in FIG. 29, the pitch of the recording width is 1.1 .mu.m+0.5 .mu.m, i.e., about 1.6 .mu.m.
The present invention was made so as to solve the above problem and has as an object thereof to provide a ROM recording medium and a recording medium functioning as a nonvolatile memory enabling an increase of the capacity of the information and an improvement of the precision of the reading of the information and an information reproducing apparatus, an information recording apparatus, and an information recording and reproducing apparatus using the same.